Stihl MS250 floods crankcase when not running

Mathias NY · Mar 9, 2014

Last fall my MS250 would run due to old gas. After cleaning the carb, it ran but tended to flood out when starting cold. Yesterday when I tried to start it for the first time in 2 months, the crankcase was filled with gas, which prevented the engine from pulling over. Has anyone else come across this type of problem before? I've worked on dozens of saws, but never had them flood when I wasn't trying to start them.

My first guesses would be a sticky needle valve and/or a bad crankcase vent. I bought the saw new about 6 years old and it has only seen about 8 tanks of fuel in that time, so a plugged vent seems unlikely. Does anyone have any other suggestions?

Thanks for the help.

94BULLITT · Mar 11, 2014

Your fuel tank vent could be clogged and letting pressure build up in the tank and push thought the carb:confused3:

Be careful cranking it over with gas in the crankcase. You could bend a rod or bust a piston.

Tollster · Mar 14, 2014

I have had sticky needle valves on motorcycles in the past, which allowed the fuel to flood the bowl, on a bike the needle valve is actuated by float height, so I think the needle valve would serve the same purpose on a saw monitoring fuel uptake, same principal, but a different design.
I typically use fine electrical wire strands for cleaning needles and small orifices on carbs if the spray doesn't seem to work.